Method of making sound reproducing diaphragms



L Iafi. 22 1 935. s. w. McKELLIP 5 METHOD OF MAKING SOUND REPRODUCING DIAPHRAGMS Filed June 10, 1952 2 sheets-sheet 1 Jan. 22, 1935. s. w. McKELLlP 1,989,015

METHOD OF MAKING SOUND REPRODUCING DIAPHRAGMS Filed June 10, 1952 2 Sheets-Sheet 2 jig-" 3.

Patented Jan. 22, 1935 UNITED STATES IVIETHOD OF MAKING SOUND REPRODUCIN G DIAPHRAGMS Spencer W. McKellip, Philadelphia, Pa, assignor to Philadelphia Storage Battery Company, Philadelphia, Pa., a corporation of Pennsylvania Application June 10, 1932, Serial No. 616,552

6 Claims.

This invention relates to conical sound reproducting diaphragms and to methods of making such diaphragms, the general object being to provide a novelly constructed diaphragm by means of a novel method.

A more specific object of the invention is to provide a diaphragm having improved frequency response characteristics and which readily lends itself to variation of such characteristics during manufacture.

A further object of the invention is to provide a diaphragm which is mechanically durable and which will retain its original shape indefinitely.

A still further object of the invention is to provide a conical diaphragm formed in one piece from a single blank of material.

Another object of the invention is to provide a conical diaphragm which readily lends itself to economical manufacture.

A further and more specific object of the invention is to provide a method of forming a. peripheral corrugated flange on a preformed conical diaphragm without weakening or breaking down the fibres of the paper or other material from which the diaphragm may be made.

Other objects of the invention will appear hereinafter. Reference may be had to the following detailed description and accompanying drawings for a full and complete disclosure of the invention.

In the drawings:

Fig. 1 is a sectional view illustrating the general construction of my improved diaphragm and the manner in which such diaphragms are commonly supported;

Fig. 2 illustrates three different forms which the peripheral corrugated flange of the diaphragm may take;

Fig. 3 is a face view of a blank of material from which the conical diaphragm may be formed;

Figs. 4 to 7 illustrate diagrammatically the manner in which the peripheral portion of the conical diaphragm is press-shaped to form the desired corrugated flange, these figures showing successive stages of the operation; and

Fig. 8 is a sectional view of apparatus in the form of a press for imparting the desired shape to the diaphragm after it has been preformed.

Various attempts have been made to provide one-piece conical diaphragms, but up to the present time, the resulting products have been more or less unsatisfactory. An attempt has been made to provide a satisfactory diaphragm by preforming a cone and providing the desired corrugated flange around the periphery thereof by bending. This method has proven unsatisfactory, however, due to various reasons which need not be pointed out in detail. It suflices to state that this method of forming the diaphragm results in weakening or even breaking down of the fibres of the peripheral portion, thereby preventing the attainment of a satisfactory product from the standpoint of efiiciency of operation and mechanical durability.

In accordance with the present invention, I provide a conical diaphragm which is superior to any such diaphragms as have been made heretofore including those mentioned above. It is known that the provision of corrugations in the body of the diaphragm at the same time that the flange is formed is desirable in some instances. The essential feature of the invention is, however, the method of forming the corrugated peripheral flange which, as is now commonly known, serves to resiliently and flexibly mount the diaphragm onits-support. The method consists essentially in preforming a cone and then press shaping the peripheral portion toprovide the desired corrugated flange.

Referring to the drawings and particularly to Fig. 1, there is illustrated in this figure a diaphragm 1 constructed in accordance with the invention, preferably having corrugations 2 in the conical body portion thereof and having a corrugated peripheral flange 3. The outer part 4 of this flange is fiat so that it may be clamped to the usual support 5 by means of clamping ring 6.

I have found that the frequency response characteristics of a diaphragm depend upon various features, the chief ones of which are the constituency of the material from which the cone is made, the angle of the cone, the corrugations of the peripheral flange, and the method of transforming the cone into the finished product. The first of these features deals, of course, with the manufacture of the paper or other material of which the diaphragm is made, and any particular frequency characteristic may be had within a wide range by modifying the constituent elements of the material and the method of making such material. The angle of the cone depends, of course, upon the design and obviously this feature may be modified at will in the making of the diaphragm. The corrugation of the peripheral flange may also be varied to impart different frequency response characteristics to the diaphragm.

In Fig. 2 of the drawings, there are disclosed three types of corrugations, the uppermost being a double corrugation, the central one being a single corrugation, and the lowermost being a triple corrugation. By varying the number of corrugations in the flange, the flexibility of the diaphragm mounting may be varied to, in turn, vary the frequency response characteristic.

While any number of corrugations may be prothat a smooth or continuously curved corrugated surface is much better, both from the standpoint of mechanical strength and efliciency of operation, than is a surface having ridges or creases. I, therefore, contemplate the forming of the cor-'- rugated surface as a smooth one throughout.

Coming now to the novel method which forms the essential part of the present invention, the first step is to provide a blank of desired shape from suitable material. Any desired and suitable material may be used, but preferably some type of paper is used to make the diaphragm. Assume ing that sheet material having the desired struc ture has been decided upon, a blank '7 (see Fig. 3) is formed from such material in any desired manner. such, for. example, as by cutting. It will be noted that this blank is circular in shape and has a sector. removed therefrom, as at 8, as well as a central opening 9. Having provided such a blank, a cone is then formed therefrom by attaching the radial edges l0v of the blank by. any suitable means, such as cement. While anyQparticular cement may be used, I prefer to use pyroxyl-in cement applied to both the radial edges which is first. allowed to dry out and then a thinner coat applied to the edges to soften the cement and enable. the desired adhesion by heating and pressure. In any. event, care should be exercised in the selection of cement, since inferior cement might cause the cone to buckle or warp.

The. next step. is to. moisten the peripheral portion of the cone which isltoibe press-shapedin the manner. described hereinafter to form the corrugated flange. This is a very important step which must be carefully performed if successful results are. to be obtained. The cone. may be moistened all overparticularly whencorrugations. are to be impressed on. it. While any suitable moisteningagent'may. beiused, I prefer to use a solution of; water. and denatured alcohol, the solution. containing about 25% alcohol when a small percentagev of sizing is contained in the paper cone. If. desired, asmallquantity of stearic acidand ammonium hydroxide may be added to thesolutionto waterproofit. The quantity of this mixturemay be about 2% of the entire solution.

The final step.in.the method is to provide the corrugatedperipheral flange on the cone and this I- do bya methodwhich I prefer to term press shapingf. Thediagrammatic illustration of Figs. 4:\td.7 Sh0WSHc1ear1y themanner. in which this step-ofithe method iscarrieduout; Referring to those. figures, 11- designatesa lower stationary ring-shaped .diemember. l2 designates anupper movabledie member. having a conical surface 13, which die member is adapted to. co-act with mer'nberlljto form the corrugated flange on the cone, thetwo die members being provided with machined corrugational surfaces 14 and 15, respectively. A central movable plug 17 is slidably positioned within the lower die member andhas itsupper end formed, as at 18, to conform with the..c'onical surface of the diaphragm and with thesurface- 13 of. die member 11. The purpose of this illustration is to clearlydisclose the mannerinlwhichthe shapingof the peripheral flange is." obtained. and not to disclose a practical apparatus. for carrying out this step, such apparatus being disclosed in Fig. 8 to be described later.

Referringstill to Figs. 4 to '7 and considering the. manner in. which the peripheral flangeis formed; die member. 12 is raised sufficiently to allo'wthe. positioning of the diaphragm 19. on the plug .1-'7,'as. shownin Fig. 4. Die member 12 is nowsbrought forciblydownward againstthe diaphragm whose central body portion is heldrigidly between member 12 and plug 1'7. Die member 12 and plug 17 are then moved downward and in .doing so member 12 co-acts with the die member 11 to provide the desired corrugated flange. It must be remembered that, the cone has had its peripheral portion moistened, as set forth above, so as to render it more susceptible to the shaping process. It is important to note that the corrugated flange is not embossed in the present method. What actually takes place when die member 12 and plug 17 are moved downward, is that when the peripheral-edge portion of the cone engages die member 11, it snaps back as illustrated in Fig. 4. As the die member 12 and plug 17 are moved further down the rounded portion 20 engages the portion 20a of the die member 11, (see Fig. 5)., and the flange is caused to. take thesshape illustrated in Fig. 6. The flange takes a corrue gational form approximating the corrugational surfaces of the dies. The approximate corrugational shape is thus imparted to. the peripheral; portion of the cone without any embossing and consequent stretching of the material taking place, the periphery being preformed, so. to. speak, as die member 12 descends. Pressure is. applied to the. preshaped cone by the dies, as shown in Fig. '7.

In Fig. 8, there is illustrated apparatus which operates according .to the above-discussed princi ples to form the cone. It will be. understood,of course, that any suitable apparatus may be used, the illustrated apparatus of Fig. 8 being merely one form of apparatus. which. may be used; to perform the. method. The apparatus. comprises essentially a. lower stationary ring-shaped die member 21, an upper movabledie member 22; and a central movable plug 23', these elements. corresponding respectively to elements 11:, 12;and',1'7. of the diagrammatic illustrations of Figs. ity to 7;. Preferably, the conical surfaces of: die member 22and; plug 23. are corrugational as. illustrated, to impart to thecentralior, body portion of theicone a corrugated: surface which has been, fgundito enhance the operation of thediaphragmiaspre: viously stated. 1

Die member 22 comprisesbody2a-and-ring:25 attached thereto. Body. 24:;15; formed; so; as to provide. a steam chamber. 26;,forheatin the die member, it being understood thatsteaIL -Qr-Qther suitable heating medium islsuppliedzt the chamber, from a suitable source. Bodr-Zrisfiilfihfilldfiii from support 2'? and the entire assembly. ablymounted for cooperationiwithqthe moyaple plus 3 and the n adie memhen 2.11.. a e: cess 28 is provided in body, 2;i at: the apexofgtlie conical surface thereof and;a.,pl ;2,9 Extent-rally located in the recess. The; apex of; plug 2;3 ;i s provided with a guide recess 30 f0 ug 29,;the recess being formed in plug-31. forming th apex; f the p u 23'. T t d d:port nfil fmlue 31 isreceived by, recess 2 8,;during; eperation of the device, to form the voice;coilsupportingmol; lar of the diaphragm. Normally;themovabledie assembly i spa d r p us 3..- u -;h:a-. dist nce as to enable the placing of the; diaphragm 19;; in inverted position over the plugas this ime, plus 23 i s-up ermqsizno itlen. bein no y u d to hatmesifioaeswfll appear more clearly hereinafter." I

The stationary ring shapeddie; member;21;is carried upon body 33 also formed;to prpyide a steam. chamber 34. Plug; 23; is; adapted; to; moye slidably. within the.diemembenand body The plug-is carried atthe upper end plfiLShaftr35 =Whflh is slidably mounted in bushing 36 and stationary collar 3'7. The shaft has attached thereto a collar 38. A coil spring 39 surrounds the shaft and is interposed between collars 3'7 and 38. Thus spring 39 normally urges the plug to its uppermost position, this action being limited by engagement of collar 38 with supporting plate 40.

In order to provide for the attachment of a cardboard or like ring 41 to the peripheral flange of the cone during the press-shaping operation, there is provided a supporting ring 42 which is resiliently mounted upon springs 43, these springs being carried by studs 44 having their lower ends threadedly secured in flange 45 of body 33.

In operation, the diaphragm is placed in inverted position upon plug 23, as above stated. If ring 41 is to be attached to the diaphragm, it is placed in position upon ring 42. The upper die assembly is now moved downward and die member 22 contacts the diaphragm to firmly hold the body thereof and to emboss the body corrugations therein, as the upper die assembly together with plug 23 now move downward and the press-shaping of the peripheral portion of the diaphragm is had in the manner above described with reference to Figs. 4 to 7. At this time, ring 41 is firmly secured to the diaphragm, it being understood that a suitable adhesive will be applied to the ring or diaphragm to effect this result. After the diaphragm is properly shaped, the upper die assembly is moved upward to a position where the diaphragm may be removed. It should be noted, however, that the corrugations formed in the body of the cone by plug 23 and die member 22 involve an embossing of the diaphragm as distinguished from the shaping of the outer peripheral flange.

It will be apparent from the present disclosure that the novel method of the invention enables the making of conical diaphragms having the various desirable characteristics hereinbefore mentioned. Obviously, various changes and modifications in the method, as well as the product, may be resorted to without departing from the scope of the invention so long as the principles set forth herein are retained. It is to be understood then that the appended claims define the scope of the invention.

I claim:

1. A method of making a conical sound reproducing diaphragm, which comprises preforming a member with a conical peripheral portion from flexible non-brittle fibrous sheet material, supporting said member throughout substantially the entire area of its body leaving only its peripheral portion free, applying a force to the edge of said portion by ground die members to cause the edge to turn back, applying a second force by said die members to the turn thus produced, applying a third force by said die members to the edge in a direction opposite that of the first two forces, whereby the peripheral portion is caused to assume an approximate corrugational flange shape, and pressing said portion into a desired corrugational flange shape.

2. A method of making a sound reproducing diaphragm, which comprises forming a conical member from flexible non-brittle sheet material, applying a force to the annular peripheral edge of said member over the entire area of said edge in a direction to cause the edge to snappingly turn back toward the body of said member, applying subsequent forces in the presence of resisting forces by grooved die surfaces to areas of said member inward of its peripheral edge and in the vicinity of the turned back portion to cause said portion to assume an approximate corrugational flange shape, and pressing said portion by the grooved die surfaces into desired corrugational flange shape.

3. A method of making a sound reproducing diaphragm, which comprises preforming a member with a conical peripheral portion from flexible non-brittle fibrous sheet material, supporting said member throughout substantially the entire area of its body leaving only its peripheral portion free, applying a force to an outer annular area of the peripheral portion by grooved die members, applying a subsequent force to an inner annular area of said portion in the presence of a resisting force by said die members to cause said portion to assume an approximate corrugational flange shape, and pressing said portion into a desired corrugational flange shape.

4. A method of making a sound reproducing diaphragm, which comprises preforming a member with a conical peripheral portion from flexible non-brittle fibrous sheet material capable of being softened by moistening, moistening said portion, supporting said member throughout substantially the entire area of its body leaving only its peripheral portion free, applying a force to an outer annular area of the peripheral portion by grooved die members, applying a subsequent force to an inner annular area of said portion in the presence of a resisting force by said die members to cause said portion to assume an approximate corrugational flange shape, and pressing said portion into a desired corrugational flange shape.

5. A method of making a sound reproducing diaphragm, which comprises preforming a member with a conical portion from flexible nonbrittle flbrous sheet material, embossing the inner part of said portion so as to provide concentric corrugations therein, supporting said member throughout substantially the entire area of its body leaving only the outer part of said portion free, applying a force to an outer annular area of said outer part by grooved die members, applying a subsequent force to an inner annular area of said outer part in the presence of a resisting force by said die members to cause said outer part to assume an approximate corrugational flange shape, and pressing said outer part into a desired corrugational flange shape.

6. A method of making a sound reproducing diaphragm, which comprises preforming a member with a conical portion from flexible nonbrittle fibrous sheet material capable of being softened by moistening, moistening said portion, embossing the inner part of said portion so as to provide concentric corrugations therein, supporting said member throughout substantially the entire area of its body leaving only the outer part of said portion free, applying a force to an outer annular area of said outer part by grooved die members, applying a subsequent force to an inner annular area of said outer part in the presence of a resisting force by said die members to cause said outer part to assume an approximate corrugational flange shape, and pressing said outer part into a desired corrugational flange shape.

SPENCER W. MCKELLIP. 

